server: add get_info tool (#26522)

* server: add get_info tool

* fix --rpc in docs

* server: harden get_info probe result handling

Report the OS as unknown when the probe process fails to spawn or times
out, so the diagnostic text from run() is never returned as an OS name.
Strip the probe output on both ends, which also drops the blank line
that ver prints before the version on Windows. Name the output and
timeout limits, and report an unreadable working directory as unknown
instead of an empty string.

* server: simplify get_info result handling

Drop the named limits and the working directory error branch, keeping
the probe result handling to a single expression.

---------

Co-authored-by: Pascal <admin@serveurperso.com>

examples/gen-docs/gen-docs.cpp

@@ -70,6 +70,8 @@ static void write_table(std::ostringstream & ss, std::vector<common_arg *> & opt
 
 static void write_help(std::ostringstream & ss, const md_file & md) {
     common_params params;
+    params.is_gen_docs = true;
+
     auto ctx_arg = common_params_parser_init(params, md.ex);
 
     std::vector<common_arg *> common_options;